Increasing numbers of methods are being employed to protect the myocardium during aortic crossclamping. Our laboratory and others have extensively studied the acute hemodynamic effects of systemic cooling, topical cooling, and potassium based cardioplegic solutions on acute left ventricular function. This year our emphasis has turned to the chronic evaluation of left ventricular function after aortic crossclamping. In addition we are measuring left ventricular function by several methods in order to determine the most sensitive and reproducible index.